In conventional sets of "iron" golf clubs, each club includes a shaft with a club head attached to one end and a grip attached to the other end. The club head includes a face for striking a golf ball. The angle between the face and a vertical plane is called "loft."
The set generally includes irons that are designated number 1 through number 9, and a series of wedges, such as a pitching wedge, a lob wedge, a gap wedge and a sand wedge. Each iron has a length that usually decreases through the set as the loft for each club head increases from the long irons to the short irons. The length of the club, along with the club head loft and center of gravity impart various performance characteristics to the ball's launch conditions upon impact. The initial trajectory of the ball extends between the impact point and the apex or peak of the trajectory. This initial portion of the ball's trajectory is of importance to golfers, because they can view it upon hitting the ball. Long irons, like the 2 iron, produce a more penetrating initial trajectory. Short irons, like the 9 iron or pitching wedge, produce an initial trajectory that is less penetrating than the trajectory of balls struck by long irons. The highest point of the long iron's ball flight is lower than the highest point for the short iron's ball flight. The mid irons, such as the 5 iron, produce an initial trajectory that is between those exhibited by balls hit with the long and short irons.
Since golfers see different initial trajectories with each iron number, golfers tend to change their swing from club-to-club in order to make the initial trajectory between clubs consistent. It would be desirable to have all the club heads in a set produce a consistent peak trajectory height along a line without requiring golfers to change their swing. This would allow golfers to use a consistent swing, which would likely improve their performance and confidence.
Therefore, it is desirable to provide a set of golf clubs that produce a substantially constant initial trajectory for the ball throughout the set.